Expansion Valve: Description and Operation

GF83.40-P-2190RC Expansion Valve, Component Description
- with CODE (580) Automatic air conditioning
- with CODE (581) Comfort automatic air conditioning

Component Identification:

Location
The expansion valve is located in the engine compartment at the left rear.

Task
The expansion valve sprays liquid refrigerant into the evaporator. The injection quantity depends on the pressure and temperature of the refrigerant supplied.

Design
The expansion valve primarily consists of the following components:
- Diaphragm (a)
- Aluminum housing (b)
- Tappet (c)
- Valve ball (d)
- Spring (e)

Function
When the refrigerant compressor (A9) is switched on, the pressure in the evaporator drops. This in turn causes the diaphragm in the expansion valve to arch. The diaphragm motion is transferred to a linkage. The plunger forces a valve ball out of its seat, which in turn opens the valve.
The opened valve enables the refrigerant to be sprayed into the evaporator. Because the motion of the diaphragm depends on the suction pressure as well as the temperature at the evaporator outlet, only the quantity of refrigerant which can evaporate optimally is injected.